One way I sort of subjectively differentiate non-great players - or players that aren't "super elite" (so right now, Sinner, Alcaraz, and Novak) - is by considering whether them not winning a Slam will be a disappointment.
In recent years, this has been true of Zverev and Tsitsipas. In my mind, they're disappointments because of their inability to bring home a Slam title. Meaning, they're good enough that it seems they "should" be Slam winners, but aren't. But guys like Fritz, Rublev, Ruud, Hurkacz, Berrettini? Not as much. Meaning, I think it would be a disappointment if Ruud and Berrettini didn't win a Masters, but not a Slam. I mean, it would be disappointing to them and their fans - but I don't think they'd be viewed historically as disappointments simply by virtue of not winning a Slam.
Similarly with players like Berdych, Tsonga, and even Ferrer. They aren't disappointments - I never really felt that any of them "should have" won a Slam. Could have? Sure, but not should. Tsonga came closest, if I remember correctly, and Ferrer had the overall steadiest career, but I can't see any of them as being disappointing. I would add guys like Raonic and Nishikori, or going back further, someone like Nikolay Davydenko. Raonic and Nishikori had somewhat disappointing careers, but more in that they didn't even win Masters; both (especially Kei) were far better players than literally dozens of guys who have won Masters in weaker eras (Portas, anyone?). Davydenko won a handful of Masters and even a Tour Final, but he never reached a Slam final and he was more in the vein of a David Ferrer: Very steady, but didn't wow people with flashes of Slam winning form.
Where am I going with this? Well, I sort of see Arthur Fils more in the category with Rublev, Ruud, Berdych, Raonic, etc - and NOT with Zverev and Tsitsipas. As of right now, at least. He doesn't look like a player that "should" win a Slam. He could...I mean, I don't think Marin Cilic was better than most of the guys mentioned in this post, but he won a Slam. But if Cilic hadn't, no one would have thought twice about it (except Cilic himself). In fact, if you look at the top 10 guys of the Big Four era, before Cilic won his, there were a half a dozen guys that could have been picked as more likely to win a Slam. In fact, before he won the 2014 US Open, Cilic was really half a step below guys like Berdych and Tsonga, and more with guys like Isner and Gasquet.
Fils is still just 20 and still improving. He made gains in 2024 and after a slow start, has done well in the last few Masters. If I were to guess who would be the next new Masters winner, he'd be near the top of the list. I think you could make an argument that aside from maybe Fonseca, he's the current Master-less player who is most likely to win a Masters at some point in his career - if only by virtue of having a lot more time than guys like Berrettini, Ruud, etc.
And again, not saying he won't win a Slam or two. He is definitely a possible Slam winner. I just don't seem him as a probable Slam winner like I do, say, Joao Fonseca or I did, Tsitsipas and Zverev.
